Traces of ancient lake found on Mars

US researchers have uncovered traces of an ancient lake on Mars boosting hopes of discovering evidence that billions of years ago the Red planet hosted life.

The lake, which dates back some 3.4 billion years, appears to have covered as much as 207 sq kilometres and was up to 500 metres deep, said the team from the University of Colorado.

"This is the first unambiguous evidence of shorelines on the surface of Mars," said Boulder research associate Gaetano Di Achille in a study published in the latest edition of Geophysical Research Letters.

"The identification of the shorelines and accompanying geological evidence allows us to calculate the size and volume of the lake, which appears to have formed about 3.4 billion years ago." Analysis of the images has shown the water carved out the canyon in which it was found, which then opened out into a valley depositing sediment which formed a delta.

"Finding shorelines is a Holy Grail of sorts to us," said assistant professor Brian Hynek, adding it showed the lake existed at a time when Mars was thought to have been cold and dry.

"Not only does this research prove there was a long-lived lake system on Mars, but we can see that the lake formed after the warm, wet period is thought to have dissipated."